1. Field of Invention
The present invention relates to the field of wind power generation. More particularly, the present invention relates to a device for detecting a crowbar circuit in the wind turbine and the method thereof.
2. Description of Related Art
With the increasing energy crisis and environmental issues, countries all over the world are vigorously developing renewable energy businesses, such as wind power generation and solar energy generation. Taking the wind power generation as an example, the installed wind power capacity in China grows rapidly, which is developed from a stall-regulated wind power system to a variable-speed and constant-frequency (VSCF) wind power system, and from a wind power system with a gear case to a direct-drive wind power system without the gear case.
However, with continuously increasing of the installed wind power capacity, after grid-connected power generation is implemented, the influence of the increased installed wind power capacity on the electrical grid cannot be simply ignored any more. For example, in order to deal with the impact of the wind turbine on the electrical grid, many countries in Europe have established new rules setting new requirements on the grid-connected wind power generation, such as controls on active power and reactive power, controls on voltage and frequency, controls on electric power quality and a low voltage ride-through function. If the grid-connected wind turbine meets these requirements, then even if the electrical grid fails (such as, voltage drops), the grid-connected wind turbine still can function without interruption, so as to provide active power and reactive power to the electrical grid rapidly, and thus the voltage and frequency of the electrical grid can be recovered and become stable timely.
Taking the direct-drive wind power system as an example, when a voltage of the electrical grid drops and the outputted voltage decreases, the outputted current has to be increased, so as to keep a balance between the power absorbed from the blower through the converter and the power transferred to the electrical grid through the converter. In general, the main circuit of the converter is often formed from a power semiconductor device such as an insulated gate bipolar transistors (IGBT) of which the thermal capacity is limited, and thus the current has to be limited. Specifically, when the dropping margin of the voltage of the electrical grid is larger, the inputted power and the outputted power of the converter are not balanced. That is, the power received from the blower through the converter is not balanced with the power transferred to the electrical grid through the converter. A common solution for the aforementioned problem includes: decreasing the power inputted by the blower; or adding a crowbar circuit for absorbing excess energy, so as to improve the short-time overload capacity of the converter at an electric machine side. When the failure is fixed and the system is recovered to be normal, the crowbar circuit is cut out from the system, thereby effectively protecting the converter.
It can be known from the above descriptions that when the power inputted into the converter from the blower is higher than that transferred to the electrical grid through the converter, a crowbar circuit can be used to absorb excess energy. However, once the crowbar circuit fails, if the system does need to throw the crowbar circuit into the system but the crowbar circuit cannot operate normally, a fatal impact on the converter will be caused, which may even cause converter scrap in a serious case.
In view of this, it is a problem desired to be solved by this industry regarding how to design a technical solution which may detect whether the crowbar circuit is normally thrown into or cut out from the wind turbine, so that an operator can locate the failure timely and precisely.